Lens blocking apparatus



July 20, 1965 L. J. PRUNIER 3,195,197

LENS BLOCKING APPARATUS Original Filed April 15, 1958 3 Sheets-Sheet 1amm lN VENTOR LOUIS J. PRUNIER ATTORNEY July 20, 1965 L. J. PRUNIER3,195,197

LENS BLOCKING APPARATUS Original Filed April 15, 1958 3 Sheets-Sheet 2fl'" I INVENTOR LOUIS J. PRUNIER ATTORN EY 3 Sheets-Sheet 3 L. J.PRUNIER LENS BLOCKING APPARATUS July 20, 1965 Original Filed April 15,1958 III- /24 mag /2 ATTORNEY United States Patent 0 3,195,397 LENSBLGCKENG AKPARATUS Louis J. Prunier, fisford, Mass, assignor to AmericanGpticai Company, oouthbridge, Mass, a voluntary association ofMassachusetts (Briginai application Apr. 15, 1958, her. No. 728,692, newPatent No. 3,H8,l8, dated Elan. 21, 196 3. Divided and this applicationApr. 8, 1963, Ser. No. 271,268

6 Qiaims. {@l. 22-58) This application is a division of my application,Serial No. 728,692, filed April 15, 1958, which has issued as US PatentNo. 3,118,198, dated January 21, 1964.

This invention relates to the blocking of lens blanks and has particularreference to the provision of improved lens blocks for holding lensblanks during the abrading thereof and means for forming said blocks andfor attaching the same to the lens blanks.

In the processing of lens blanks, particularly of the multifocal typewhich are to be provided with toric surface curvatures on one or both oftheir sides, it is imperative that the major and minor axes of the toricsurfaces be precisely on the cylinder axis desired and in the case ofbifocals, properly aligned relative to the respective seg ment portionsof the blanks in accordance with the prescriptive requirements of thefinished lenses to be formed from the blanks.

in order to detachably support and maintain individual lens blanks inpredetermined accurate alignment with the various pieces of apparatususually required to perform the several operations necessary to producefinished optical surfaces of the above character on the blanks, it hasbeen the practice heretofore to provide individual blocks formed of castiron, steel, aluminum or the like and to attach each of the lens blanksto a respective block with a blocking medium such as pitch or othersuitable adhesive.

While this practice has successfully provided means for accuratelymaintaining individual lens blanks in predetermined aligned relationwith apparatus used to form the desired surface curvatures thereon, ithas been found that lens blocks of the above character are relativelyexpensive to manufacture, require separate and precision assembly withthe blanks and in order to be reusable, the blocks must be thoroughlycleaned upon completion of each surfacing operation to remove the pitchor other blocking medium which remains on their lens mounting surfacesafter the lens blank-s are removed therefrom. The cleaning ofconventional lens blocks involves a tedious and time consuming taskwhich in combination with the initial cost of the blocks, increases theoverall expenditures required to manufacture prescriptive lenses or lensblanks of the above character.

The present invention provides not only improved apparatus by which lensblanks of the above character may be more economically manufactured butalso novel lens blocks which, in addition to being formed in attachedrelation with the blanks, simultaneously insure accurate axial relationof said blanks with the means subsequently used in forming the desiredfinished optical surfaces thereon.

It is accordingly an object of the invention to provide simplified,highly effective and economical means for the precision blocking of lensblanks as well as new and improved lens blocks.

Another object is to provide an improved lens blocking techniqueincluding means for molding or otherwise forming individual lens blocksdirectly upon lens blanks which are to be surfaced and in proper axialposition on said blanks.

Another object is to provide means for blocking lens blanks by forminglens blocks directly upon a side surface 3,11%,lh? Patented July 20,1965 ice of the lens blanks which blocks are formed of a low meltingmetallic alloy characterized by the fact that when hardened it isadapted to withstand normal temperature changes incurred duringconventional abrading operations without softening or otherwisedistorting.

Another object is to provide novel means of blocking lens blanks byforming metallic blocks attached to the blanks without the use ofconventional blocking materials and which blocks are simultaneouslyformed with connection means for detachable assembly with the abradingapparatus for forming the desired abraded surface on said blanks and forsupporting said blanks in precision axial position during said abrading.

Another object is to provide lens blanks with rigid and relativelydurable lens blocks formed of a metallic material which in itself willprovide secure holding and aligning means for the lens blanks and whichmaterial is readily reusable upon completion of the lens blank surfacingoperation.

Another object is to provide novel means for simultaneously blocking alens blank and providing locating means on the lens block, whichlocating means is adapted to be subsequently accurately interfitted withaxis aligning members of conventional lens surfacing devices so as tomaintain a lens blank being surfaced in predetermined axially alignedrelation with the lens forming tools of said devices.

A further object is to provide means for obviating the time-consumingblock cleaning procedures common to conventional lens surfacingoperations by forming lens blocks in attached relation with the blankswithout the use of conventional blocking materials from a low meltingblocking material of the above character which may be indefinitelyrepeatedly melted and reformed in accordance with the invention withoutrequiring reconditioning of the material or incurring any appreciableloss of said material.

Other objects and advantages of the invention will become apparent fromthe following description when taken in conjunction with theaccompanying drawings in which:

FiG. l is a perspective view of a blocked lens blank illustrating onetype of lens block such as results from the practice of the invention;

H6. 2 is another perspective view of a blocked lens blank illustratinganother type of lens block of the invention;

FIG. 3 is a diagrammatic illustration of one form of lens surfacegenerating device used in the processing of lens blanks which have beenblocked in accordance with the invention;

FIG. 4 is a fragmentary cross-sectional view taken on line ltof FIG. 3;

FIG. 5 is a diagrammatic illustration of means for finishing thegenerated surfaces of lens blanks in accordance with the invention;

FIG. 6 is a fragmentary enlarged cross-sectional view taken through theapparatus of FIG. 5 substantially along line 6-6 thereof and looking inthe direction of the arrows;

FIG. 7 is another fragmentary cross-sectional view of a part of theapparatus of FIG. 5 taken at a position which is indicated by line 7-7of FIG. 6 and looking in the direction of the arrows:

FIG. 8 is a cross-sectional view of a blocked lens blank of the typeillustrated in FIG. 2 shown in a position of use;

FIG 9 is a face View of a marked lens blank which is typical of those tobe blocked in accordance with the invention;

FIG. 10 is an enlarged longitudinal cross-sectional view of a part ofthe lens generating apparatus of FIG. 3 upon which is provided means forforming a lens block 3 of the type embodying the invention and furthermeans for receiving and aligning a lens blank which is to be attached tosaid block;

FIG. 11 is an end or face view of the lens block form ing portion of.the device of FIG.

FIG. 12 is a fragmentary longitudinal cross-sectional view of a modifiedform of the device illustrated in FIG.

FIG. 13 is a side elevational view, partially in section, of'a blockingdevice which is used in conjunction with the apparatus of FIGS. 10 and11 to carry out the method 'of' the invention;

FIG. 14 is an enlarged view taken at a location indicated by line 1414of FIG. 13 and looking in the direction of the arrows; and

FIG. l5'is a longitudinal cross-sectional view of a modified part of thegenerating apparatus of FIG. 3 which is adapted to receive lens blankswhich have been blocked in accordance with the invention.

In thedrawings, wherein like characters of reference designate likeparts throughout the various views there is shown in FlG. 1 a lens blankattached to one type of a block 21 which has been formed on the lensblank 20 in accordance with the practice of the invention so as toprovide holdingand aligning means for detachably mounting the lens blank20 in'abrading relation with lens surfacing apparatus such as shown inFIGS. 3 and 4. 7

It will become apparent from the description to follow that the lensblock 21 need not be restricted to the form shown in'FIG. 1 but may beprovided in various other shapes or configurations and a preferredmodification of the block 21 is illustrated in FIG. 2 wherein a lensblank 22 is provided with a differently shaped block 23 also formed inaccordance with the invention.

The lens blocking technique of the invention, which includes the blocksresulting therefrom, is designed and intended to carry out in a unique,more efiicient and economical manner, the well-known procedure involvedin providing lens blanks with prescriptive curvatures on one or both oftheir side surfaces and in proper axial position.

It is the general practice in the manufacture of lenses, to 'select'lens blanksfrom stock which have been initially provided with anoptically finished spherical surface on one of their sides andasemi-finished or cleared" surface on their opposite sides. 'Theoptically finished curvature on a lens blankis generally referred to'asits base curve and its opposite or semi-finished side is subsequentlyprovided with a surface shape which is either spherical or toric andwhich, in combination with the base curve, indexof refraction andresultant thickness of the finished lens, is such as to satisfy theprescriptive requirements of a particular individual to use the same.

It is the finishing of the second side of the lens blanks with which thepresent invention is primarily concerned, regardless of whether thesecond side is to be provided with a spherical shape or the more complextoric shape or whether the lens blanks are of the single vision or themultifocal type.

' For purposes of best illustrating this invention, the more complicatedprocess of finishing the second side of a bifocal lens blank which is tobe provided with a toric surface will be discussed hereinafter. i

In FIG. 9 there is shown a plan or face view of a bifocal lens blank 24which has been marked in the conventional manner to indicate the point25 at which the optical center of the lens blank is to be ultimatelylocated and the dotted lines 26 indicate the direction in which the axisof cylinder curvature is to be provided on the lens blank 24.

It will be noted that for purposes of illustration, the segment part 28of the lens blank 24 has been decentered a distance x from thegeometrical center 27 of the blank and the cylinder axis 26 of the toricsurface to be provided on the blank is disposed at an angle y relativeto the horizontal axis of the blank.

Since in most instances, the segment part 28 is placed on the convex orplus side of a lens blank and the finished base curve is also providedon the plus side of the lens blank, the lens blank must be blocked onits plus side and finished by surfacing its concave or negative side.Such a case will be described hereinafter with reference to the lensblank 24 but it should be understood that in specialcases' wherein thebase curve of a lens blank is provided on its concave side and itsconvex side is to be finished, the lens blank will of course be blockedon its concave side.

.The first step in surfacing a lens blank which has been blocked is torough generate or abrade the side thereof to be surfaced with apparatusof the general character shown in FIG. 3. While various types ofmachinery may be used for this purpose a machine of the type disclosedin detail in Patent No. 2,548,418 issued April 10, 1951 to D. P.Bernheirn et al. will be discussed herein.

Referring more particularly to FIG. 3 it can be seen ,thata rotatablecupped type abrading tool 39 is provided to abrade the lens blank 2-4 byswinging across the face of the lens blank 24 about a pivot point 31which is adjust- .a'bly controlled to cause the abrading edge of thetool 24 to describe a curved path 32 having a radius of curvature 33precisely that desired of the spherical or base curvature of theprescription toric surface to be provided on the concave side of thelens blank 24 and the diameter of the abrading face of the tool 36 iscontrolled to automatically and simultaneously produce the desiredcylindrical curvature of the toric surface along a meridian normal tothe meridian or axis of the spherical or base curvature. The lens blank24 is held in abrading relation with the tool 30 by means of a blocksuch as 21 or 23 (FIG. '1 or 2) which is securely held in predeterminedaxially aligned relation with the tool 30 by means of a work bar 34having an elongated body part 35 and a chuck-like end part 36. The bodypart 35 of the work bar 34 is held securely in a magnetized V groove 37formed in a stationary part 38 of the generating apparatus so as tocause the central'longitudinal axis 4% of the work bar 34'.- to passthrough the pivot point 31 of the tool 36. A longitudinally adjustablescrew mechanism 39 is provided on the part 38 of the apparatus in such amanner as to engage the end of the work bar 34 opposite its chuck 36 andprovide adjustable means for moving the work bar and lens blank 24toward the tool 36 in accordance with the depth of cut desired on thelens blank which ultimately determines the final thickness of thefinished lens blank.

It should be appreciated that with lens generating apparatus of theabove character, the lens blank 24 must be accurately mounted in thechuck 36 with its-optical center 25 precisely aligned coincident withthe axis 40 which passes through the pivot point 31 of the tool 30 andthe axis'of' cylinder curvature 26 of the lens blank must be aligned andheld precisely in parallel relation with the plane in which the tool 30swings about point 31.

In order to provide simple, efficient and highly accurate means formaintaining the lens blank 24 in the above mentioned alignment on theapparatus of FIG. 3 and in similarly aligned relationwith the tool partsof other apparatus such as shown in FIGS. 5, 6 and 7 during subsequentfinishing operations on the lens blank, the invention provides theimproved lens blocks (21 M23) which may be molded separately and appliedto a work bar such as 34 or preferably formed directly on the work barin the following manner.

Referring more particularly to FIGS. 10 and 11 whens-l in 'one form ofthe invention is illustrated which is adapted to provide lens blankswith blocks of the type illustrated inFIG. 1, the chuck-like end part 36of the work part 34 is provided with a mold cavity 41 surrounded by anannular lens blank supporting ring 42 havassess? U7 ing a relativelythin or knife-like outer edge 43 adapted to receive the opticallyfinished side surface of the lens blank 24 in the manner illustrated inFIG. 10. The cavity 41, which is shown filled with a block formingmaterial in FIG. 10 and empty in FIG. 11, is provided with a pair ofdiametrically opposed inwardly extended recesses 4 which, when filledwith a blocking material in the manner shown in FIG. 10, will form ablock having a pair of diametrically opposed extensions 45 (FIGS. 1 and10) each having a depression 46 therein, which extension 4-5 anddepressions 46 are to function as axis aligning means for use insurfacing the lens blank in a manner to be described in greater detailhereinafter.

The depressions as are formed by pin members 47 which are each providedwith an end part 48 of a shape complementary to that which is desired tobe reproduced in the finished lens block. It will be noted that forpurposes of illustration, the ends 4-8 of the pin members 4'7 are shownspherical in shape so as to ultimately provide the block 21 with concavespherically shaped depressions 46. However, it should be clear that theends 48 of the pin members 47 could be made conical or provided with anyother shape in accordance with that which is desired of the finallyformed depressions 46.

The ends 43 of the pin members 47 extend through openings in theenlarged end 49a of a supporting part 49 of the chuck-like end 36 of thework bar 34, which part 49 forms the base of the mold cavity 41. Theends 48 of the pin members 4-7 protrude into their respective recesses44 an amount sufiicient to ultimately provide a full semicirculardepression in each of the extensions 45 of the finished block 21 whichare of a depth therein substantially equal to the radius of curvature ofthe ends as of the pin members 47. The opposite ends of the pin members47 are each press fitted or otherwise fixed in a floating collar whichis longitudinally slidable along an elongated necked-down portion 51 ofthe supporting part 49. Intermediate the ends of the supporting part 49,the necked-down portion 51 is provided with a threaded area 52 on whichis mounted an internally threaded stop ring 53. The stop ring 53 isthreadedly adjusted along the threaded area 52 to a position such asshown in PEG. which will limit the extent to which the collar St} andits attached pin members 47 may be drawn away from cavity 41 thusproviding adjustable locating means for controlling the extent to whichthe ends 48 of pin members 47 may be permitted to extend into therecesses 4-4 of the mold cavity 41 when the collar 50 is fully retractedagainst the stop ring 53 as illustrated. When finally adjusted, the ring53 is clamped to the part 49 by a set screw or the like 54. Alsothreadedly engaged upon the part 49 is a hollow sleeve 55 which isadapted to straddle the stop ring 53 and engage the annular edge partsof the collar 59 in the manner shown in FIG. 10 wherein the sleeve 55will be free to rotate about the collar 5% but will carry the collar Slllongitudinally along the necked-down portion 51 of the part 49 when itis advanced along the threaded area 52 by being rotated about to thepart 49. In order to align the cylinder axis 26 of a lens blank such asshown in FIG. 9 in aligned relation to an axis extending through thecenters of the two diametrically opposed pin members 47 and tosimultaneously align the center of the ens blank with the central axisof the work bar 34, indicia in the form of cross lines 56 and 57 areprovided inside the mold cavity ll on the uppermost surface 4% of thepart 4d. The line 56 is provided in accurately aligned relation with animaginary line extending through the centers of the pin members 47 andthe line 57 is located to extend in a direction normal to the line 56and intersect the line 55 at a point through which the central axis 40of the work bar extends (see FIG. 11). Thus, by placing the finishedside of the lens blank 24 in contact with the supporting ring 42 andmanually adjusting the lens blank to locate its optical center 25coincident with the intersection of lines 56 and 57 and simultaneouslyaligning the axis 26 of the lens blank in parallel relation with theline 57, the lens blank is ready to be blocked. Since it is often timesdifiicult to obtain a clear view of the indicia 5s and 57 through thematerial of a lens blank, particularly when shaded or colored lensblanks are used, the lines 56 and 57 are formed as slits which extendinto a cavity 58 provided centrally within the member 49. In thisinstance the cavity 58 is filled with a transparent lighttransmittingplastic or the like 59 and a communicating opening 6% is providedthrough the side Wall of the part 59 through which light may beprojected from an external source 61 (FIG. 10) into the plastic 59. Aninclined reflecting surface 62 is provided on the plastic at its endwhich is adjacent the communicating opening 69 to direct the lightoutwardly through the plastic material and slits which form the lines 56and 57 and thus illuminate the lines 56 and 57 so as to render the samemore readily visible through the lens blank.

Because the work bar 34 is not only used to block the lens blank but isalso used to support the lens blank during the generating of its surfacecurvature with the apparatus of FIG. 3, it is pointed out that thechuck-like end part 36 of the work bar 3 is accurately fitted into oneend of the elongated body part 35 with the central axes of both parts 35and 36 in coincident relation with each other. A tapered opening 63 isprovided in the body part 35 into which the tapered end 64 of the chuckpart is accurately fitted. in order to cause the imaginary lineextending through centers of the pin members 47 (which imaginary line isin normal relation with the cylinder axis 2d of a lens blank mounted onthe chuck part 36) to be disposed in normal relation to the direction orplane in which the tool 3% (FIG. 3) swings about point 31 as discussedabove, the body part 35 of the work bar is provided with a pair of flatsides .5565 and 3519 (FIG. 4) which locate the work bar in the V groove37 of the apparatus of PEG. 3 and prevent the work bar 3 3 from rotatingtherein during a generating operation. The tapered end 64 of the chuckpart 36 is provided with a locating pin 65 which keys into a mating slot66 in the body part 35. The slot 56 and pin 65 are so located relativeto the flats 35a and 3522 as to automatically properly align theabove-mentioned imaginary line which extends through the pin members 47relative to the tool 36 when the chuck 36 and body parts 3% of the workbar 34 are assembled as illustrated in FIG. 10 and positioned on theapparatus of FIG. 3 in the manner illustrated more particularly in FIG.4.

The blocking of the lens blank 2 on the work bar 3% is accomplished withthe apparatus of FIG. 13 which comprises a base 67 upon which is mounteda support, generally indicated by numeral 63, for holding a work bar 34upon which a lens blank 24 is to be mounted. The support 63 embodies apair of spaced upstanding parts 69 and "it? each of which are providedwith V grooves 6% and 753a respectively in which the work bar 34 isrested during the blocked operation. The V grooves 6% and 7% areidentical in cross-sectional shape to the above mentioned V groove 37 ofthe generating apparatus of PEG. 3 so that the fiat sides 35a and 35b ofthe work bar 34 will seat against the sides of the V grooves 69a and7th: and locate the work bar S in a position on the blocking apparatussimulating the position it assumes when placed in abrading relation withthe apparatus of PEG. 3. The support 68 is further provided withdepending bearing parts 71 and 72 which are pivotally connected by a rod73 to a pair of bosses vs and 75 which are integrally formed with orotherwise secured to the base 67. To one side of the support 68 there isprovided on the base 6'7 an upstanding bracket 76 upon which is iounteda dispensing apparatus 77 having means for storing and dispensing aliquefied blocking medium which is used to fill the mold cavity ll inthe work bar 34. The dispensing apparatus embodies an outer supportingshell or enclosure 73 formed or" sheet metal or the like rigidly securedto the bracket 75, which supports'a tank 79 con taining a supply ofWater 8% which is heated by means of conventional submersible electricalheating elements or the like 81. Within the tank 79 there is provided asecond tank or container 82 in which is provided a supply of blockingmaterial 83. The container 82 extends a considerable distance below theupper water level of the tank 79 which is usually maintained atapproximately the location illustrated in FIG. 13 and openings 84 areprovided in the container 82 to allow the water 80 to circulate thereinas illustrated.

The blocking material 83 which may consist of any substance such asplastic or metal alloy material having the characteristics of a lowtemperature melting metallic alloy known to the trade as Cerro-low orCerro-bend manufactured and sold by Cerro de Pasco Co. is placed in thecontainer through its upper open end which is provided with a cover 85having a wire basket 86 or the like attached thereto. By lifting thebasket 36 out of the water along with the cover 85, pieces of solidblocking material such as previously formed blocks or the like whichhave been removed from finished lens blanks may be placed in the basketand lowered into the water 83 which is heated by heating elements 81 toa temperature sufficient to melt the solid blocking material. When thesolid blocking material is melted by the heat of the water 80, it willrun through the weave of the basket 86 and collect in the bottom of thecontainer 82 in the manner shown in FIG. 13. 'Being heavier than waterit will, of course, displace any water which might be in the bottom ofthe container 82. If for any reason pieces of glass, paper or otherforeign material happen to be attached to the solid blocking materialwhen it is deposited in the basket 86, it can be seen that when meltedin the basket, the blocking material will flow through the weave of thebasket and substantially allof' the foreign material will be left in thebasket 86 where it may be easily removed. An outlet is provided for themelted blocking material 83 in the bottom of the container 82 and thisoutlet is in the form of a pipe or tubular member 87 extendingvertically substantially throughout the length of the container 82 anddown into the lower part of the tank 79 where it is connected by'afitting 88 to a valve mechanism 39 also mounted within the internallower part of the tank 79. It will be noted that the upper part of thetubular member 87 functions as a guide means for supporting the basket86 centrally within the container 82 and the tubular member 37 isprovided with openings 90 adjacent the bottom of the container 82 whichallow the melted blocking material 83 to flow downwardly from thecontainer 82 through the tubular member 87 and into the valve mechanism89. The valve mechanism 89 is provided with a nozzle 91 which extendsforwardly and outwardly of the enclosure 78. Within the bore 92 of thevalve mechanism 89 there is provided a longitudinally adjustable plunger93 which is normally in the position indicated in PEG. 13 where itslowermost end part closes the exit opening 94 through the nozzle 91. Theplunger 93 is held in closed relation with the nozzle 91 by means of anactuating mechanism embodying a relatively short lever arm 95 which islinked with the uppermost end of the plunger 93 and fixed to a shaft 96which is rotatably mounted in the enclosure 78. An operating lever 96awhich is directly, rigidly connected to shaft 96, extends forwardly ofthe apparatus of FIG. 13 to a location slightly above the nozzle 91 andis spring biased in an upward direction by a coil spring 97 to normallyurge the plunger 93 against the exit opening 94 of the nozzle 91. Bymoving the forward end of the lever 9a downwardly toward the nozzle 91against the tension of the spring 97, it can be seen that the lever arm95 will e rotated counterclockwise as viewed in FIG. 13 and the plunger93 will be drawn away from the exit opening 94 of the nozzle 91 to allowthe blocking material 83 to Q or bularmember87 and valve mechanism 89,in which the blocking material 83 is located, are completely surroundedat all times with the water 89 which is maintained at a'temperaturesufiicient .to keep the blocking material 83 in its melted state andfree flowing. It should als-obe appreciated that since the blockingmaterial can be completely melted or liquefied at a temperature rangingbetween approximately 117 to 156 Fahrenheit which is approximately thetemperature to which the water is heated, an operator of the blockingmechanism is completely safe from injury even though he may accidentallyhave physical contact with the melted blocking material or the water inthe container '79.

I11 order to block a lens blank on a work bar 34 with the apparatus ofFIG. 13, the support 68 is first swung outwardly in a siclewisedirection away from the nozzle 91 by pivoting the same about the rod 73whereupon the work-bar 34- is placed in the V grooves 69a and a thereofin the manner disclosed above with its flat parts 35a and 35b seatedagainst the respective sides of the V grooves. By swinging the support68 outwardly in this manner the work bar 34 may be quickly and easilyproperly placed in the V grooves 69a and 70a. The support 68 is nextswung back toward the nozzle 91 against a'stop $8 whichprojectsoutwardly of the bracket '76. The stop 93 is preferably in the form of ascrew or the like which is threadedly adjustable in the bracket 76 butadapted to be locked by a lock nu-t or the like, not shown, so as toextend from the bracket an amount suflicient to locate the exit opening94 in the nozzle 91 directly above the longitudinal axis of the work barwhen the support 68 is in contact with the stop 98. i

After the support 63 is positioned against the stop 98, the work bar 34is moved in the direction of its longitu-- dirial axis along the Vgrooves dim and 79a to a position where the enlarged end part 49a of thework bar contacts a second stop 99 in the manner illustrated in FIG. 13.The second stop 99 is fixed to the upstanding part 69 of the support 68and function cooperatively with the stop 98 to locate an opening 109(see FIG/1 0), in the part 4% which communicates with the mold cavity41, in accurate alignment with the nozzle 91 so as to permit theblocking material 8-3 to flow from the nozzle 91 dire'ctly intothe' moldcavity 41 when the 1ever 96a is op era-ted as mentioned above. i v iAfter the support 68 and work bar 34 have been adjusted relative to thestops 9S and 99as described above, a clamp member 101 carried by thebracket '76 is clamped tightly against the body part 35 of the work barto hold it and the support 68 securely in the above-mentioned alignedrelation with the nozzle 91.

A lens blank 24 to be blocked is then placed against the supporting ring42 and aligned relative to the lines or indicia 56 and 57 so as to haveits optical center 25 aligned on axis with the point of intersection ofthe indicia 56 and 57 and its cylinder axis 26 also aligned with theline or indicia 57 in the manner disclosed in detail hereinabove andshown in FIG, 14. Sighting means embodying a peep sight 102 and a pairof plane reflecting mirrors 163 and 104 are provided on the base 67 andthe enclosure 78 to aid in accurately aligning the lens blank with the'indicia S6 and 57 and to overcome the efiects of parallax which mightresult from the spacing between the indic-ia 56 and 57 and the alignmentmarkings 2S and 26 on the lens blank. 7 I g If the indicia 55 and 57 arenot normally clearly visible through the lens blank.24, a light may bedirected into the opening 60 so'as to illuminate the indici-a 56 and 57which are formed as slits through the base of the mold cavity 41. 7

When the lens blank 24- is accurately aligned with the indicia 56 and 57on the work bar 34, a spring urged clamp arm v195 is placed against theouter surface of the lens blank 24 to hold it securely against thesupporting ring 42 of the work bar 34-. The clamp arm 105 is at agents?9 tached with a swivel connection 106 to the forward end of the rod 73and a spring 197 which is placed under compression between a stop member1% carried by the rod 73 and the adjacent side of the bearing part '71.The spring forcefully urge the clamp arm 1&5 against the lens blank 24.

The mold cavity is next filled with the blocking material 83 bydepressing the lever %a so as to open the valve mechanism 89 and allowthe blocking material to flow through the nozzle 91 directly into thecavity 4-1 through the communication or opening 1% therein. When themold cavity 4-1 is completely filled the lever 96a is released to stopthe flow of blocking material.

Referring more particularly to H6. 10, the blocking material is suchthat when the mold cavity is filled and as the said material hardens itnot only becomes attached to the lens blank but also forms the block forthe blank and it is simultaneously provided with the recesses 46therein. The said recesses being in proper positional relation with thecylinder axis of the surface to be formed on the blank.

When the blocking material 33 has cooled and becomes solidified in themold cavity 41 in the clamp arm 1&5 and the clamp member 161 arereleased and the support 68 is swung away from the nozzle 91 whereuponthe work bar 34 is lifted from the support 63.

It is pointed out that cooling means such as circulating cold water orthe like could be applied to the outer part of the mold cavity 41 toprovide a more rapid cooling and hardening of the blocking material 83.However, it has been found that with the apparatus shown and described,the material 83 will harden relatively quickly without applying acoolant at the blocking station and will not cause any appreciable delayin removing the work bar from the blocking apparatus.

After the lens blank 24 is blocked to the work bar 34 and the bar 34 hasbeen removed from the apparatus of FIG. 13 it is placed on the apparatusof FIG. 3 and the exposed surface of the lens blank is generated in themanner disclosed in detail hereinabove. It is pointed out that duringthe generating of the lens blank surface, a coolant is applied to thelens blank which flows over the mold part of the work bar This cool-antprovides a final cooling of the mold and lens block formed therein whilesimultaneously dissipating the heat produced by the generating of thelens blank surface.

Following the operation Winch is performed by the apparatus of FIG. 3the lens blank and its attached block 21 are ejected as a unit from themold cavity 41 in the work bar 3 3- by rotating the sleeve 55 in adirection which will cause it to advance along the threaded area 52toward the mold cavity 41. In so doing, the collar t which is carried bythe sleeve 55 will cause the pin members 47 to force the block 21 andits attached lens blank out of, and away from the cavity 41.

Upon removal from the work bar 34, the generated surface of the blockedlens blank 24 is optically finished by fine grinding and polishingoperations which are performed on surfacing apparatus of the typediagrammatically illustrated in FIGS. 5, 6 and 7 in which a forming toolor lap it}? is provided with a lens blank forming surface which isaccurately shaped to the curvature desired on the surface of the lensblank 2 A resilient aligning mechanism 111, which embodies a yoke member1 12 having a pair of depending axis aligning pins 113 therein, issupported over the lap roe by resilient arm parts 114 so as to cause anaxis through the pins 113 to be held at all times in precise parallelalignment with the spherical axis of the curvature provided on thesurface 11d of the lap it While permitting the yoke 112 to be movedabout the surface 11$ of the lap by operation of a crank arm 115 whichis provided with a drive pin 116 sealed in a recess which is disposedcentrally in the yoke 112. By placing the lens blank directly upon thesurface 111? of the lap 1% is illustrated, and causing the pins 113 toengage the recesses as which have been formed in the block 21 attachedthereto, the spherical axis which has been generated by the apparatus ofFIG. 13 will be accurately aligned parallel to the spherical axis of thecurvature of surface illtl. The finish abrading and polishing of thelens blank 2 is brought about in a Wellknown manner by applying asuitable abrading or polishing medium between the engaging surfaces ofthe lens blank 24 and lap 31%? while moving either the lens blank or thelap, or both, relative to each other.

it should be clear that the lens block 21 not only replaces theconventional cast iron type of lens block which must be attached to alens blank with pitch or the like, but also provides axis aligning meansin the form of recesses 26 which are simultaneously formed in oneoperation with the forming of the block.

Upon completion of the polishing operation the lens blank 24 is removedfrom the block by simply squeezing the sides of the block together witha suitable tool so as to distort its shape slightly. This will cause thelens blank to be immediately released. Alternatively, the blank may beremoved from the block by shocking the blocked lens blank with a slightbut sharp blow or, the material of the block can be melted away from theblank. It is preferable, however, to deblock by following the firstmentioned method of squeezing and distorting the lens block.

After each deblocking operation, the material of the used block isreclaimed and rendered reusable by placing it in the heated water 530 ofthe blocking mechanism as discussed above. In this manner no waste ofthe blocking material is incurred and it is pointed out that thetechnique of the invention overcomes the usual expense of replacing wornor damaged blocks since the blocks of the invention are only used tocarry out one lens blank surfacing procedure whereupon they are meltedand reformed each time a lens blank is blocked.

t should be clearly understood that the shape of the lens blocks andlocation of the aligning recesses :26 therein are entirely dependentupon the type of mold in which they are formed and the mold may bedesigned to form blocks which would be adaptable to lens surfacingapparatus of types other than these illustrated herein. For example, ifthe second or unfinished side of stock lens blanks were to be providedwith spherical curvatures only, the blocks would preferably be formedwith only one cenral recess which would be used to receive the drive pin116 of a surfacing machine such as shown in FIGS. 5 through 7 or a lensblock 23 such as shown in FIG. 2 could be provided with an insert 117 inthe manner illustrated in FIG. 8 wherein the drive pin 118 would engagethe center of the block 23.

In PEG. 12 the work bar 34 of FIG. 9 is illustrated as embodying meansfor blocking lens blanks which are to ultimately be provided with aprescriptive prism correction. That is, where one side of a lens blankis to be finished thicker than its diametrically opposed side along apredetermined axis through the optical center of the lens blank. t willbe noted that the annular lens blank supporting ring l2- of FIG. 10 hasbeen replaced by another lens supporting ring 120 which is constructedto be higher at one side than it is at its diametrically opposed side soas to cause the general plane of the lens blank 24a to be inclinedrelative to the longitudinal axis of the Work bar 34 an amount inaccordance with the difference in height of the above mentioneddiametrically opposed sides of the ring 126. it is evident that byblocking a lens blank 24a on the Work bar 34 in this tilted or inclinedmanner that more material will be removed from its highest side thanwill be removed from its lowest side when the concave surface thereof iscurve generated with the apparatus of FIG. 3 and this will introduce theabovementioned prism eifect in the generated lens blank.

Several rings 12;? are provided with various degrees of inclined lensmounting edges in accordance with the degree of prism correction desiredof the finished lens blank l. l and are readily and quickly replaceableupon the work bar 34. Rings 12% and 42 are each provided with an annulargroove 122a into which L-shaped clamps 122 are fitted as shown in FIGS.10 and 12 and the clamps 122 are secured to the enlarged end 49a of thesupporting part 49 of the chuck 36. In this manner, the ring 12% may berotated about its axis.

The ring 120 which is rotatably mounted on the work bar is rotated anamount sutficient to align an axis extending between the highest andlowest points on the ring 120 with respect to the indicia 56 and '7 soas to determine the axis along which the prism correction will bedirected. This is done in accordance with the prescriptive requirementsof the particular lens blank being blocked.

When the ring 120 is properly rotationally aligned on the work bar 34,the lens blank 24a. is blocked in exactly the same manner as the lensblank 24 which was discussed previously.

It should be appreciated that the blocks and lens blanks attachedthereto may be ejected from the work bar 34 of FIG. 13 immediatelyfollowing a blocking operation and applied to other work bars such asshown in FIG. 15 for performing the lens blank surface generatingoperation illustrated by FIG. 3.

. The Work bar of FIG. 15 is provided with a vacuum chuck 123 which isprovided with a cavity 124 of substantially the same outer contour shapeas the lens block 21 and is further provided with aligning pins 125which are adapted to engage the recesses 46 of the block 21 when theblock 21 is fitted into the cavity 124. A vacuum line 126 is directedinto a hollow area 127 behind the cavity 124 and by continuallyevacuating the air from the area 127 by known means, the lens block willbe held securely in aligned relation with the work bar during a surfacegenerating operation.

It is also pointed out that the blocking mechanism, FIG. 13, may beprovided with a permanent blocking mold to replace the apparatus whichsupports the work bar 34. In such a case, the lenses would be blockedand then ejected from the mold whereupon they would next be applied to awork bar such as shown in FIG. 15 for subsequent processing.

While it has been described above that the block is formed in directcontact with the lens blank, in instances when a metal is used, the sidesurface of the lens blank to be blocked may be initially provided with arelatively thin, preferably transparent, coating of plastic materialsuch as polyvinyl chloride or the like. The block in such an instance isformed in contact with the plastic coating which is initially brushed onto the surface of the blank.

The plastic material is such that while it provides a good bond betweenthe blank and block it may be peeled off the surface of the blank orblock without leaving any residue thereon after the blank has beensurfaced and removed from the block.

'From the foregoing, it will be seen that improved simplified andeconomical means have been provided for accomplishing all of the objectsand advantagse of the invention. However, it should be apparent thatmany changes in the details of construction,.arrangement of parts andsteps of the invention may be made by those skilled in the art withoutdeparting from the spirit of the invention as expressed in theaccompanying claims and the invention is not to be limited to the exactmatters shown and described herein as only the preferred matters havebeen given by way of illustration.

Having described my invention, I claim:

1. Apparatus for blocking lens blanks comprising mold means for forminga lens block, said mold means having an open ended cavity thereincontoured to define the shape desired of that part of a block to beattached to a lens blank which is to be gripped by lens blank processingmeans, a lens blank receiving seat extending peripherally about the openend of said cavity for receiving a side surface of said lens blank,indicia within said cavity with which said lens blank may be alignedwhen positioned on said seat, means protruding into said cavity in.predetermined aligned relation with said indica to provide recessedlocating means on said block for use in locating said lens blank in saidlens blank processing means subsequent to blocking of said blank, saidmold means having an opening through a side thereof giving access tosaid cavity when said side of said lens blank is placed on said seat forpermitting a block forming material to be introduced into said cavity toform said block in connected relation with said side of said lens blankand means for ejecting said block from the open end of said'mold meanssubsequent to its being formed therein.

2. Apparatus for blocking lens blanks comprising mold means for forminga lens block, said mold means having an open ended'cavity thereincontoured to define the shape desired of that part of a block to beattached to a lens blank which is to be gripped by lens blank processingmeans, a continuous lens blank receiving seat extending peripherallyabout the open end of said cavity for receiving a side surface of saidlens blank, indicia within said cavity with which said lens blank may bealigned when positioned on said seat, means for releasably holding saidlens blank in said aligned position on said seat, means protruding intosaid cavity in predetermined aligned relation with said indicia toprovide recessed locating means on said block for use in locating saidlens blank in said lens blank processing means subsequent to blocking ofsaid blank, said mold means having an opening through a side thereofgiving access to said cavity when said side of said lens blank is placedon said seat for permitting a fiowable block forming material to beintroduced into said cavity, means for containing and dispensing asupply of 'said block forming material, supporting means for saidcontaining and'dispensing means and means for positioning said openingin said mold means in predetermined aligned relation beneath saiddispensing means, means for actuating said dispensing means'to permitsaid block forming material to flow doW-nwardlythrough said opening andinto said cavity .to form said block in connected'relation with saidside of said lens blank and means in said mold means for ejecting saidblock from the open end of said cavity subsequent to its being formedtherein.

3. Apparatus for blocking lens blanks comprising mold means for forminga lens block, said mold means having an open ended cavity thereincontoured to define the shape desired of that part of a block to beattached to a lens blank which is to be gripped by lens blank processingmeans, a lens blank receiving seat extending peripherally about the openend of said cavity for receiving a side surface of said lens blank,indicia within said cavity with which said lens blank may be alignedwhen positioned on said seat, means within said mold means forpermitting said indicia to be illuminated, adjustable means protrudinginto said cavity in predetermined aligned relation with said indicia toprovide recessed locating means on said block for use in said lens blankprocessing means said lens blank subsequent to blocking of the blank,said adjustable means being contoured to the shape desired of saidlocating means,

said mold means having an opening through a side thereof giving accessto said cavity when said side of said lens blank in' placed on said seatfor permitting a block forming material to be introduced into saidcavity to form said block in connected relation with said side of saidlens blank and means for advancing said adjustable means into saidcavity an amount suflicient to eject said block from the open end ofsaid mold means subsequent to its being formed therein.

4. A work bar for blocking and supporting lens blanks to be abradedcomprising an elongated body member, locating surfaces on said bodymember for use in locating the body member in a lens blank processinmeans, and mold means on one end of said body member for blocking a lensblank to said Work ba said mold means having an open ended cavitytherein contoured to define the shape desired of that part of a block tobe attached to a lens blank which is to be gripped by another lens blankprocessing means, said cavity having its central axis aligned with thelongitudinal axis of said body member, a continuous lens nk receivingseat extending eripherally about the open end of said cavity forreceiving a side surface of a lens blank to be blocked, indicia withinsaid cavity with which said lens blank may be aligned when positioned onsaid seat, means protruding into said cavity in predetermined alignedrelation with said indicia to provide recessed locating means on saidblock when formed in said cavity for use in locating said lens blank insaid other lens blank processing means subsequent to blocking of theblank, said mold means having an opening through a side thereof givingaccess to said cavity, when said side of said lens blank is placed onsaid seat for permitting a flowable block forming material to beintroduced into said cavity to form said block in connected relationwith said side of said lens blank and means in said mold means forreleasing said block and attached lens blank from said w rk bar wherebysaid lens blank can be successively located in lens blank processingmeans by reference to said body member and to said block.

5, Apparatus for blocking lens blanks comprising mold means for forminga lens block, said mold means having an open ended cavity thereincontoured to define the shape desired of that part of a block to beattached to a lens blank which is to be gripped by lens blank processingmeans, a lens blank receiving seat extending peripherally about the openend of said cavity for receiving a side surface of said lens blank,adjustable means protruding into said cavity in predetermined alignedrelation with said indicia to provide recessed locating means on saidblock for use in locating said lens blank in said lens blank processingmeans subsequent to blocking of the blank, said adjustable means beingcontoured to the shape desired of said locating means, said mold meanshaving an opening through a side thereof giving access to said cavitywhen said side of said lens blank is placed on said seat for permittinga block forming material to be introduced into said cavity to form saidblock in connected relation with said side of said lens blank and meansfor advancing said adjustable means into said cavity an amountsnfficient to eject said block from the open end of said mold meanssubsequent to its being formed therein.

6. Apparatus for providing a lens block on a lens blank comprising moldmeans having a mold cavity open at one end in which a rigid lens blockis adapted to be formed, said cavity being contoured to mold asubstantial part of the desired shape of a lens block formed thereinincluding that part of said lens block subsequently to be held by lensblank processing means, said cavity being contoured to release a rigidlens block molded therein from within said cavity, said mold meanshaving a lens blank receiving seat about said open cavity end forreceiving one side of said lens blank so that said blank cooperates withsaid mold cavity to define the remainder of the desired shape of saidlens block, said mold means having an opening giving access to said moldcavity when said lens blank is placed on said seat, and means forintroducing block forming material into said cavity to form a lens blockhaving said desired shape in connected relation With said side of saidlens blank.

References Cited by the Examiner UNITED STATES PATENTS 2,465,153 3/49Fritzsclie 51-277 2,781,547 2/57 Moxness 1830 2,930,130 3/60 Ray et al.51-277 MICHAEL V. BRINDISI, Primary Examiner.

6. APPARATUS FOR PROVIDING A LENS BLOCK ON A LENS BLANK COMPRISING MOLDMEANS HAVING A MOLD CAVITY OPEN AT ONE END IN WHICH A RIGID LENS BLOCKIS ADAPTED TO BE FORMED, SAID CAVITY BEING CONTOURED TO MOLD ASUBSTANTIAL PART OF THE DESIRED SHAPE OF A LENS BLOCK FORMED THEREININCLUDING THAT PART OF SAID LENS BLOCK SUBSEQUENTLY TO BE HELD BY LENSBLANK PROCESSING MEANS, SAID CAVITY BEING CONTOURED TO RELEASE A RIGIDLENS BLOCK MOLDED THEREIN FROM WITHIN SAID CAVITY, SAID MOLD MEANSHAVING A LENS BLANK RECEIVING SEAT ABOUT SAID OPEN CAVITY END FORRECEIVING ONE SIDE OF SAID LENS BLANK SO THAT SAID BLANK COOPERATES WITHSAID MOLD CAVITY TO DEFINE THE REMAINDER OF THE DESIRED SHAPE OF SAIDLENS BLOCK, SAID MOLD MEANS HAVING AN OPENING GIVING ACCESS TO SAID MOLDCAVITY WHEN SAID LENS BLANK IS PLACED ON SAID SEAT, AND MEANS FORINTRODUCING BLOCK FORMING MATERIAL INTO